A conventional liquid oxygen (LOX), liquid hydrogen (LH.sub.2) rocket engine is shown in FIG. 1. Liquid hydrogen is the engine's fuel and liquid oxygen the engine's oxidizing agent. In a conventional rocket engine, the fuel and oxidizer's standing head, from reservoirs or tanks 140 and 145, provide the motive force which allows the LH.sub.2 and LOX to flow through the fuel turbo pump 100 and oxidizer turbo pump 105 and into a gas generator 110. Once LH.sub.2 and LOX mix in the gas generator 110, they combust providing further motive force to spin-up the fuel and oxidizer turbo pumps, 100 and 105.
Once this (boot-strap) process is begun, the fuel turbo pump 100 provides liquid hydrogen through adjustable valve 115, orifice 120 and mixer 125 to the combustion chamber 130. Similarly, the oxidizer turbo pump 105 provides liquid oxygen through orifice 120 and adjustable valve 115 to the combustion chamber 130. Within the combustion chamber, LH.sub.2 and LOX combust creating an exhaust gas which flows into the thrust chamber 135 and out the jet nozzle.
In addition to being used as fuel, a small fraction of the LH.sub.2 is used to cool the exterior of the combustion and thrust chambers, 130 and 135 respectively, and as a result is heated. Liquid hydrogen, heated in this process, is routed to mixer 125 where it is combined with cooler LH.sub.2 (i.e., that portion of liquid hydrogen not used for cooling) before it is fed into the combustion chamber 130. The purpose of the mixer 125 is to "homogenize" the temperature of the LH.sub.2 fed into the combustion chamber 130.
Orifices 120 provide coarse control of LH.sub.2 and LOX flow through the rocket engine. Adjustable valves 115 provide fine control of LH.sub.2 and LOX flow through the rocket engine.